A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1344000 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 14 15 16 20 21 24 25 28 30 32 35 40 42 48 50 56 60 64 70 75 80 84 96 100 105 112 120 125 128 140 150 160 168 175 192 200 210 224 240 250 256 280 300 320 336 350 375 384 400 420 448 480 500 512 525 560 600 640 672 700 750 768 800 840 875 896 960 1,000 1,050 1,120 1,200 1,280 1,344 1,400 1,500 1,536 1,600 1,680 1,750 1,792 1,920 2,000 2,100 2,240 2,400 2,560 2,625 2,688 2,800 3,000 3,200 3,360 3,500 3,584 3,840 4,000 4,200 4,480 4,800 5,250 5,376 5,600 6,000 6,400 6,720 7,000 7,680 8,000 8,400 8,960 9,600 10,500 10,752 11,200 12,000 12,800 13,440 14,000 16,000 16,800 17,920 19,200 21,000 22,400 24,000 26,880 28,000 32,000 33,600 38,400 42,000 44,800 48,000 53,760 56,000 64,000 67,200 84,000 89,600 96,000 112,000 134,400 168,000 192,000 224,000 268,800 336,000 448,000 672,000 and 1,344,000, with no remainder.
Since 1,344,000 cannot be divided by just 1 and 1,344,000, it is not a prime number.